The Gemara asks: What is Hanukkah, and why are lights kindled on Hanukkah? The Gemara answers: The Sages taught in Megillat Ta’anit: On the twenty-fifth of Kislev, the days of Hanukkah are eight. One may not eulogize on them and one may not fast on them. What is the reason? When the Greeks entered the Sanctuary they defiled all the oils that were in the Sanctuary by touching them. And when the Hasmonean monarchy overcame them and emerged victorious over them, they searched and found only one cruse of oil that was placed with the seal of the High Priest, undisturbed by the Greeks. And there was sufficient oil there to light the candelabrum for only one day. A miracle occurred and they lit the candelabrum from it eight days. The next year the Sages instituted those days and made them holidays with recitation of Hallel and special thanksgiving in prayer and blessings.

From the Gemara's answer it is implied that the main miracle that Chanukah commemorates is the miracle of the flask of oil that burned for eight days and not the victory of the Jews over the Greeks.

It is true that the victory occupies a prominent place in our daily prayers but the incident of the oil seems to be the primary reason that the sages instituted the holiday of Chanukah. Yet, as we see so often throughout the Torah, that it's words are sparse in one place and rich in another place. The background of this festival of lights is related elsewhere; in Mesechta Meilah, Daf 17a.

The Roman government had once issued a decree that Jews might not keep the Sabbath, circumcise their children, and that they should have intercourse with menstruant women. Thereupon Rabbi Reuven son of Istroboli cut his hair in the Roman fashion, and went and sat among them. He said to them:If a man has an enemy, what does he wish him, to be poor or rich? They said: That he be poor. He said to them: If so, let them do no work on the Sabbath so that they grow poor. They said: ‘He speaketh rightly’, let this decree be annulled. It was indeed annulled.Then he continued: If one has an enemy, what does he wish him, to be weak or healthy? They answered: Weak. He said to them: Then let their children be circumcised at the age of eight days and they will be weak. They said: ‘Hespeaketh rightly’, and it was annulled.Finally he said to them: If one has an enemy, what does he wish him, to multiply or to decrease? They said to him: That he decreases. If so, let them have no intercourse with menstruant women. They said: ‘He speaketh rightly’, and it was annulled.Later they came to know that he was a Jew, and the decrees were re-instituted.​Let's think about this. What were the Romans thinking when they instituted the decree; what were their thoughts after Rabbi Reuven son of Istroboli in the guise of a Roman outlined his logic, and above all, what were they thinking after his masquerade was discovered, that they re-enacted that which they annulled?Harav Moshe Levin, Rabbi of Netanya explains: the Romans came to the conclusion that when it comes to the Jews, standard rationale doesn't apply. Jews are above logic. What seems to work and be good and considrered progress in the eyes of (pagan) society is a drawback and obstacle to the Jews. They have different guages; what is beneficial to the nations is disastrous by the Jews. What the nations of the world see as passivity, to the Jews is active and obligatory. There is nothing the world can offer to the Jew.This explains why the original rationale of Rabbi Reuven son of Istroboli worked, the Romans were working with the world's standards: one who doesn't work one day a week is not utilizing the opportunity to make more money and will become peverty-stricken. Likewise, one who circumsizes his son weakens him and the same applies to marital relations, if one is not engaged in bringing children into the world, he is causing the population to decline. They therefore agreed to annul the decree to weaken the influence of the Jews as per Rabbi Reuven son of Istroboli who made the claim that with such decrees the Jewish People will prosper.Once it was discovered that it was a Jew, they had second thoughts and realized that the regular laws of nature are reversed when dealing with the Jews. They therefore re-instituted the decrees as their experience showed them; that taking away the natural order is the only way to damage the Jews.This story sheds light as to why the sages chose the miracle of the oil over the miracle of the unnatural victory of the Jews over their enemies. Since the Jews work with their own set of rules and the miracle of the oil best represents the Jewish outlook of the world, where the Laws of Nature don't play a role.